The present invention relates to an insulated vessel which may be produced at low cost, has superior insulating capabilities and excellent volumetric efficiency, and which may be suitably employed in a thermos, cooler, icebox, insulated cup, thermal insulated lunch box, thermal insulated electric pot, heat retaining rice cooker, refrigerator or freezer box material, or as an insulating layer in a bath tub.
Insulated vessels are conventionally available having a double walled structure wherein the space interval between the outer vessel and the inner vessel is filled with an organic foaming material such as hard urethane foam or foaming polystyrene, or a fabrication thereof, or is filled with an inorganic powder such as perlite.
Also conventionally available is a vacuum insulated vessel wherein the space between the inner vessel and the outer vessel of a double walled vessel consisting of a metallic inner vessel and a metallic outer vessel joined in an integral fashion is vacuum sealed to form a vacuum insulating layer.
However, in the former insulated vessel, because the coefficient of thermal conductivity of the insulating material itself is large compared to the case of a vacuum insulation, it is not possible to obtain a high degree of insulating capability. Further, problems also exist with respect to the production and capabilities of this vessel in that, because it is necessary to make the insulating layer thick (more than several centimeters) the vessel has a small ratio of inner volume to the outer volume. That is to say, volumetric efficiency is reduced.
Furthermore, while the latter vacuum insulated vessel has excellent insulating capabilities, an insulating layer of a small thickness, and large volumetric efficiency, the production process is complicated. Accordingly, high production costs are incurred.